In general, a dental implant is an artificial tooth root that replaces a missing tooth of a patient. The dental implant is installed and incorporated to a toothless site of the alveolar bone and then is fixed to the alveolar bone in order to replace a missing tooth root and recover the original function of the tooth. Here, the dental implant is made of a biocompatible alloy of for example titanium.
A dental implant procedure generally involves several surgeries such as incising and peeling the soft tissue and drilling the bone for installation of the implant, installing the implant, and constructing an upper prosthesis. The surgeries for incising and peeling the soft tissue are not significantly different from the principle of a typical periodontal surgery. The surgery of drilling the bone generally includes a process of drilling the cortical bone and drilling the cancellous bone. The bone drilling surgery involves, according to the basic principles thereof, trimming the bone near an implant site, marking the implant site, and drilling a small hole in the cortical bone, followed by gradually enlarging the hole up to a diameter substantially the same as or slightly smaller than that of an implant to be installed.
Then, the implant is installed after the alveolar bone of a patient is drilled using a bone cutting tool such as a drill. The drilling of the alveolar bone is a very important procedure, which takes a long time and is difficult to perform.
Now, a brief description will be given of a typical drilling process performed for implant installation. Firstly, the upper part of the alveolar bone is drilled around the toothless site, followed by enlarging of the opening. A surgical guide, fabricated to locate and orient the implant, is mounted to the alveolar bone. While alveolar bone is being watered, the implant site is marked on the surface of the alveolar bone by using an initial drill such as a point drill. The point drill is replaced with a first drill, which in turn enlarges the upper part of the hole while the alveolar bone is being watered. Through such procedures, the hole having a predetermined depth is drilled and becomes gradually enlarged from a small diameter to a larger diameter. The first drill is replaced with a final drill, which in turn enlarges the lower part of the hole while the alveolar bone is being watered. The final drill is then replaced with a tap drill to form threads in the hole while the alveolar bone is being watered. Next, a fixture is coupled into the thread hole using a certain tool, an abutment is fastened to the fixture, and then an artificial tooth is fixed to the abutment using adhesive.
A considerable number of patients have an oral structure which makes it difficult to perform the implant surgery. Particularly, this is the case where only a small amount of bone matrix remains in the posterior area near the maxillary sinus. In this case, the maxillary sinus membrane or, briefly, sinus membrane is lifted to secure a space, a bone graft is placed in the secured space, and a dental implant is embedded in this space. This method is classified into a vertical approach and a lateral approach.
First, the vertical approach (osteotomy) is a method that is used when a bone matrix in a target area for implant surgery is secure to some extent (the thickness of the bone matrix is 4 mm or more), in which method the maxilla is tapped several times with an osteotome (a chisel and a hammer), forming a hole having a diameter from 2 mm to 3 mm, and graft bone material is inserted little by little through the hole. This method has the benefit that a patient has little edema after the surgery because of the narrow target surgery area. However, negatives come from the facts that since the dentist cannot directly see the sinus membrane, he/she has to perform surgery very carefully, checking the membrane with X-ray images, which is time-consuming, thereby prolonging the surgery, and also the patient experiences severe discomfort due to the tapping performed during the surgery.
Next, the lateral approach is a method that is used when a very small amount of bone matrix remains in a target area for implant surgery (the thickness of the bone matrix is 4 mm or less), in which method the maxilla is drilled to form a hole (window) in a lateral side so as to lift the sinus membrane, and bone grafting is carried out through the hole. The method has an advantage in that, since the dentist can lift the sinus membrane and directly view it during the surgery, the membrane is seldom damaged, and further in that, even if damage to the membrane occurs, post-treatment for dealing with the situation is possible, and the desired quantity of bone graft can be laid quickly at one time, so that the processing is implemented quickly. However, the method also has a problem in that the surgery itself is difficult to perform, and a larger valve should be provided, so that severe edema may occur after the surgery. Accordingly, dentists avoid performing such a method in practice.
Recently, in addition to the above methods, a maxillary sinus lift method using a common implant drill and a trephine drill have been recently researched. The method using the implant drill has advantages in that it can minimize the discomfort of patients and is fast to perform. However, at the moment that the maxilla is completely bored by the rotation of the drill blades, the tips of the drill blades can come into contact with the sinus membrane. Since there are no means for preventing the drill blades from contacting the sinus membrane, there is a high risk that the sinus membrane can be torn or damaged by the drill blades. Accordingly, there are demands for solutions that can overcome these problems.
As a conventional approach, Korean Patent No. 0619145, titled ‘Implant Drill for Sinus Membrane Lift,’ was proposed. The implant drill of the above identified patent is an implant trephine drill form being mounted onto a common dental handpiece. The implant drill has a cutting groove on one end of a tubular body, a central shaft with a shank and a protrusion member elastically positioned in the body so as to protrude and retract in the longitudinal direction in the central portion of the cutting groove of the body end. The protrusion member is inserted into the tubular body and is supported by a spring. Further, the protrusion member has a projection and the tubular body has a projection on the inside wall thereof, so that the projections engage with each other, thereby securing the protrusion member from becoming detached out of the tubular body.
However, in the conventional drill for sinus membrane lift, the protrusion member is integrally provided to the outer circumference of the tubular body, thereby reducing an effective drilling area. Further, since the drill has a sophisticated construction, it is difficult to fabricate the drill or disassemble/assemble the drill for sterilization after surgery.
In particular, efficient drilling is difficult since the tubular body acting as a drilling component is supported by the spring. Further, there is a risk that the sinus membrane may be damaged by a sharp front edge of the protrusion member.
Another conventional approach is to lift the sinus membrane using a piezoelectric device, which uses minute vibration in place of rotation to drill the bone. In this approach, since hard bones can be efficiently drilled but soft tissues are not easily drilled, the maxilla can be drilled without damaging the sinus membrane.
However, this approach has drawbacks in that too much time is spent to drill the bone and there is no measure to control the depth to which the drill is inserted into the maxillary sinus. A thick compact bone takes too much time for drilling, which is somewhat worrisome. Further, there is a risk that a surgeon may apply an excessive force so excessively that the drill can be pushed into the maxillary sinus, thereby tearing or damaging the sinus membrane.